The present invention relates to a fixing device for use in, for example, a copying machine, a laser beam printer or a facsimile. The present invention also relates to a temperature control method for the fixing device, and an image forming apparatus that employs the fixing device.
In a conventional fixing device, a noncontact temperature sensor has detected a surface temperature of a heating and fixing roller in a position located apart from the surface of the heating and fixing roller (refer to JP 11-223555 A).
In the conventional fixing device, therefore, the noncontact temperature sensor has belatedly detected the surface temperature of the heating and fixing roller. This has caused a problem that the surface temperature of the heating and fixing roller and the detection temperature of the noncontact temperature sensor differ from each other. Accordingly, it has been difficult to stably adjust the temperature of the heating and fixing roller on the basis of the detection temperature of the noncontact temperature sensor. Therefore, the fixed image performance has not been stable.
The noncontact temperature sensor also detects the temperature of the atmosphere in the neighborhood of the noncontact temperature sensor. Therefore, the detected temperature varies depending on the sensor placement distance from the heating and fixing roller, variation of the environmental temperature, the warming degree of the fixing device or the like. As the result, it has been difficult to stably adjust the temperature of the heating and fixing roller with use of only the temperature detected by the noncontact temperature sensor, since those temperature variations cannot be correctly predicted.